This protocol utilizes three subsets of participants: healthy non-diabetics, subjects with impaired glucose tolerance, and type 2 diabetics who are hyperglycemic. The purpose of the study is to examine total hepatic glucose production and gluconeogenesis and relate them to hepatic enzymes. It will also examine insulin-medicated total body glucose metabolism and plasma free fatty acid and glycerol concentrations and their relation to molecular and biochemical events in the muscle which are mediated by muscle. Finally, it will compare measures of insulin action in liver, muscle, and adipose tissue.